Pole changer control circuit



April 13, 1943.

B. A. WALLACE POLE CHANGER CONTROL CIRCUIT Filed Oct. 30, 1940 ILA/PM CON 7'? 0L P045 CHANGER sum Patented Apr. 13, 1943 POLE CHANGER CONTROL CIRCUIT Bert A. Wallace, Chicago, Ill., assignor to Kellogg Switchboard and Supply 111., a corporation of Illinois Company, Chicago,

Application October 30, 1940, Serial No. 363,489

9 Claims.

This invention relates to pole changers and more particularly to a pole changer control system.

In the telephone art, it has been the practice to provide a plurality of sources of different frequency ringing currents. If a single pole changer or set of pole changers is utilized, and for some reason or other it becomes defective or inoperative, it then becomes impossible to ring a subscriber. To avoid such a. condition, the use of duplicate pole changers has been resorted to. With either duplicate or individual pole changers, a relatively heavy starting current is needed to begin the operation of the frequency ringing device or pole changer.

One feature of the present invention is to maintain these bell ringing pole changers vibrating at all times to avoid the need of frequent heavy starting currents.

With duplicate pole changer circuits wherein the secondary ringer is used only when the primary ringer is inoperative, the primary ringer will take all of the normal wear and the secondary ringing device Will be almost continuously idle. It is, therefore, desirable to alternate the use of these duplicate pole changers so as to distribute the wear on the equipment.

If, in the alternate use of the ringing equip ment, one or the other of the pole changer becomes defective or inoperative, an attempt to apply ringing current from that source Would be ineffective to call the subscriber. Thus, it is desirable to provide test and selection means so that if one of the pole changers is defective, the other always will be used.

One object of this invention is to provide a ringing circuit having duplicate pole-changers which are normally used alternately, means being provided whereby, if one of the pol changers should become inoperative, the other will always be employed.

Another object is to provide a multiple frequency ringing source wherein any inoperative pole changer is cut out and an operative pole changer is applied for each different frequency, at all times, whereby an operative source is always available. A further object is to eliminate heavy starting currents and no-load primary currents.

A feature of this invention is the provision of alarm control which will indicate the inoperative condition of any one of the ringin devices.

Another feature of this invention is to obtain the foregoing desirable results by means of a relatively simple pole changer control system. Yet

frequency ringing current another feature resides in the provision of means whereby any good pole changer for any frequency can be used in any group. Other features and advantages will appear from the following desscription taken in connection with the accompanying drawing.

Although this system is described and illustrated with a single frequency ringing station, it is to be readily understood that the system is equally applicable to multiple ringing frequencies since the circuit diagram for the additional ringing frequencies would be a mere addition to that shown.

In the drawing, a single figure is used showing a preferred circuit diagram to illustrate the features of this invention.

Referring to the drawing, means for providing but a single frequency ringing current is shown, comprising two alternative pole changers; to wit, pole changer IA and pole changer IB. The primary of ringing transformer HT is arranged to be connected to one or the other of the pole changers by means of appropriate switching means, and the secondary of the ringing transformer is joined, by suitable conductors SI and S2, to a subscribers circuit to be rung.

In the preferred system, the duplicate pole changers IA and B are constantly running since their operating current is a small fraction of the starting current. The output from either pole changer need only be connected to a line to ring the subscriber. Thus, the need for automatic starters is eleminated.

This system is especially useful where five frequency harmonic ringing is used, portions only being duplicated for each frequency. The entire system is adapted for unattended dial exchanges, or manual exchanges. I

A pole changerstarting relay I is used toinitiate the application of ringing current to a subscribers line. Other relays and switches are utilized, to alternate the use of the pole changers, to test the pole changers for operativeness, and to select an operative pole changer for ringing purposes.

A more detailed description of the operation of this device will be given to illustrate its preferred manner of use.

What may be called the normal operation of the circuit will first be described. This is the operation in which the duplicate sources of each are properly working and are being alternately used during a ringing period.

Relay I has its winding connected to ground by either a ringing relay, or manually, to operate armatures I and II. Armature II] at its front contact places ground on an intermediate or center tap MP of the primary P of its ringing transformer RT Energizing potential of the proper frequency is alternately applied at the opposite terminals PI and P2 of the primary over a circuit traced from grounded battery, through reed RI, its right contact, armature I2 of relay and its back contact, back contact and armature I3 of relay 1 to P I thence to MP and through the front contact and armature I0 of relay I to ground; or from grounded battery through reed RI, its left contact, armature I4 and back contact of relay 5, conductor I5, back contact and armature I6 of relay I to P2, thence to MP and through the front contact and armature III of relay I to ground. The above application of energizing current to the primary of transformer RT causes alternating ringing current to flow in the secondary. This current actuates relay 6 to remove armature I'I from its back contact.

When relay I operates, a circuit for relay 3 is completed to ground at armature II of relay I. Relay 3 operates and moves its armature I8 against its front contact. Armature I'I being open, nothing operates.

Armature H also closes a circuit from ground through armature II and front contact of relay I, conductor I9, armature and back contact of relay 6, conductor 2| and through the winding 2A of relay 2 to battery and ground. Relay 2 operates, closing its armature 22 and front contact. The ringing continues until terminated by release of relay I which in turn removes the ground for the ringing transformer and relay 2. This in turn releases relay 6.

The removal of ground at armature I I does not release relay 2 because ground on winding 4A of relay 4 is supplied over armature 22, thereby causing relay 4 to operate, locking both 2 and 4 until the next application of ringing current is to be made.

Upon the next call for ringing current, relay I again operates to place ground on conductors 24 and I9. Relays 2 and 4 being held from the previous operation, ground on conductor I9, passes through operated armature I9, to conductor 25 to operate relay 5; which latter disconnects IA at armatures I2 and I l, and substitutes IB at its front contacts and armatures 26 and 2'1. This places the energizing current from IE on the ringing transformer by alternately effective circuits from grounded battery, reed R2, armature 2B and its front contact, conductor 23, armature I3 to P! to MP, and conductor 29, armature 21 and its front contact, conductor 30, back contact and armature I6 and P2 to MP, and thence by conductor 25 to armature I9 and ground. The application of ringing current again operates relay 6 to open contacts I6 to prevent closure of the alarm circuit and the circuit of slow relay I at armature I8 of slow-operating relay 3.

On this call for ringing current, coils 2B and 4B of relays 2 and 4 are energized. The circuit of 2B is from grounded battery, through conductors SI and 32, winding 23, front contact and armature 33 of relay 2, conductor 3%, front contact and armature 2B of relay 4, conductor I9 and armature II to ground; and the circuit of 4B is from grounded battery, conductors 3|, 35, and

36, winding 43, parts 34, 20, I9, and II to ground. The energization of 2B counteracts the effect of 2A thereby restoring the difierential relay 2 to open the circuit of 4A and 2A at 22 and 2B at 33. The winding AB holds relay 4.

At the end of the ringing, relay I is again released, thereby restoring relays 3, 4, and 5. The latter substitutes IA for IE. Relay 6 restores responsive to the cessation of ringing current resulting from the opening of the primary circuit at armature III.

The foregoing operation covers the alternate use of IA and IB for ringing as long as these devices are functioning normally. The same mode of operation applies to the four other duplicate frequency sources where a five frequency harmonic system is used.

The secondary terminals SI and S2 of each ringing transformer will be connected to the line to be called. The secondary terminals of each ringing source will be selectively connected by a suitable multiple frequency switch control, not shown. These other frequency sources are multiplied cn the control circuits MI, M2 and M3. The alternating control by relays I, 2, 3 and 4 will be common to the entire group, with each set having its controlled, corresponding terminals SI and S2.

During what may be termed the normal operation of the device, the duplicate pole changers are alternately used as described. This alternation of use is applicable at all times and where one or the other of the ringing sources is defective, the alternation also takes place, but in such a case, if the defective pole changer happens to be the one connected for ringing, the relay I shifts the connection to the operative ringing pole changer, as will be described. The use of a pole changer out of its normal alternate use when one of the ringing sources is defective, does not alter the basic operation. In other Words, the sources are alternately applied and the substitute use of one for the other does not interfere with this cyclic operation.

The operation of the system will now be further described, considering first that IA is inoperative and then that the pole changer IB is inoperative.

Assuming the pole changer IA to be inoperative, and starting with pole changer IA about to be used for the next ringing operation, relays 2 and 4 are in restored condition, and the system functions as follows: Relay I is energized and by its armatures It and II places ground upon the conductors 24 and I9. This, in turn, completes the energizing circuit for slow-operating relay 3 and for operating coil 2A of relay 2. It also places the ground on the ringing transformer RT over conductor 24. With the connected pole changer IA defective, the application of ground to the primary of the ringing transformer fails to cause ringing current to flow in the secondary windings. In this case, relay 6 is therefore not actuated, thereby leaving armature I1 closed. Then, when slow-operating relay 3 operates, a moment later, it closes a circuit as follows: from ground, through contacts I8, conductor 23, contacts Ii, conductors 38 and 39, contacts controlled by armature 42, conductor 39, relay I, to battery. Relay I thereupon operates. At armature 152 it locks itself directly to conductor 23, independent of contacts IT, at the same time opening its initial circuit, while at armature 4| it applies ground potential to alarm conductor 3?. At armatures I3 and I6, relay I shifts the outer terminals of the transformer primary P from the defective pole changer IA to pole changer IB. Assuming the pole changer IE to be operating properly, ringing current is immediately applied over conductors SI and S2. This application of ringing current immediately energizes relay 6, removing ground at contacts I1 from conductor 38 which extends to the alarm circuit. Pole changer IE will continue to serve, for relay I remains locked to conductor 23.

Upon the termination of the ringing operation, relays I, 6, 3, and 1 restore, and relay 4 operates in the locking circuit of relay 2 to prepare for the next operation to be that of IE.

The apparatus is now in the condition with relays 2 and 4 held in operated position by coils 2A and 4A. With the beginning of a new ringing operation, relay I is again energized. Relay 5 thereupon operates over conductor I9, contacts I9 and conductor '25 to substitute IB for IA, differential relay 2 restoring as hereinbefore described.

Since pole changer IB is operative, relay 5 is energized barring an application of ground to relay 1 by slow-operating relay 3. With the termination of this ringing period, relays I, 4, 5, 6, and 3 release as hereinbefore described. The apparatus is now in condition for a further ringing call which would connect the currently defective pole changer IA, as previously described, with the consequent substitution of IE.

Let it now be assumed that pole changer IA is operative and IB is inoperative, and that the next pole changer to be connected up is IA. The operation of relay I places ground on the ringing transformer with the resultant energization of relay 6 and the application of ringing current. With relay 6 operated, the operation of slow relay 3, when it occurs, is without effect. Relay 2 operates as hereinbefore described, to prepare for the operation of relay 4 when relay I again restores.

Upon the termination of the ringing operation, relay I is deenergized, resetting the apparatus and operating relay 4 for the next operation. On the next operation of relay I, relay 5 is operated through contacts I9 to substitute device IB, in its regular turn, for device IA. With device IB defective, as assumed, no ringing current flows over leads SI and S2. Relay 6, therefore, fails to operate, permitting relay 1 to operate as before described. Relay I energizes the alarm conductor 31 and at armatures I3 and I6 shifts the transformer terminals PI and P2 to the stand-by leads, to which operative device IA is now connected, through armatures I2 and I4, and their front contacts. Ringing current now flows over leads SI and S2, operating relay 6 to disconnect ground from alarm lead 31. Relay 1, however, remains locked to conductor 23, independent of contacts I1.

All of the illustrated relays of the system restore when relay I next falls back, preparing for the starting of a new cycle of operation.

As will be apparent from an inspection of the drawing, when relay I has been operated to substitute the other one of the devices IA and IB for the one currently connected, through armatures I2 and I4 or through armatures 26 and 21, to the back contacts of armatures I3 and I6, and the second pole changer is likewise defective, relay 6 is not operated by this second pole changer, in which case ground potential remains applied to alarm control conductor 31 to sound any suitable alarm. The circuit for applying ground potential to alarm control conductor 31 is from ground through armature I8 and its front contact, over common conductor 23, through armature I1 and its back contact, over conductor 38,

and thence through armature M of relay 1 and its front contact, to conductor 31.

It will be observed that each of the conductors 23, 24, and 25 extending upwardly from contacts of relays 3, I, and 4, respectively, has a symbol applied thereto indicating that such conductor is common to a plurality of sets of equipment, one of which is shown. The illustrated set of equipment includes pole changers IA and IB, relays 5 and I, ringing transformer RT, test relay 6, and ringing leads SI and S2. Leads 23, 24, and 25, therefore, are indicated as extending to other similar sets of ringing equipment, each of which includes 'a pair of pole changers, such as IA and i5. This fact is further indicated by the arrowheaded extensions of conductors 23 to 25 labeled M3, M2, and MI, respectively. It will be understood, therefore, that the set of ringing equipment illustrated above the common equipment comprising relays 2, 4, I, and 3, is only one of a plurality of such sets of ringing equipment, each of which contains its own provisions for alternating the use of the pair of pole changers and for substituting the other pole changer in the event that the one currently connected up is defective, as indicated by a failure to operate of the relay therein corresponding to relay 5. One advantage of this device is that the ground connection is only placed on the ringing transformer when it is to be used. This reduces the no-load primary current in the system, even with the vibrators operating.

A further advantage is due to the continuous operation of the pole changers. Heavy starting currents are eliminated upon each application of ringing current. The open primary circuit also eliminates no-load current in the transformer.

Another advantage resides in the application of a good pole changer in every frequency set upon every application of ringing current.

Although the preferred embodiment of this invention is illustrated and described, variations within the true spirit and scope of the same will be determined by the appended claims.

Having thus described my invention, what I claim is new and desire to secure by United States Letters Patent is:

1. In a ringing-current supply system, a pair of alternative pole changers for controlling the flow of ringing current, switching means for applying either pole changer to the system to the exclusion of the other, means periodically effective for operating said switching means to substitute the other pole changer for either currently applied one, means for testing each newly applied pole changer to determine its condition, and means controlled by said test means responsive to an abnormal condition of the newly applied pole changer for operating said switching means to reverse the substitution.

2. In a ringing-current supply system, a pole changer for controlling the flow of ringing current, said pole changer including a vibratory arm and contacts alternately closed thereby, circuit connections including said contacts for supplying ringing current to said system, said circuit connections being open when ringing current is not needed, means for maintaining said arm in vibration at all times whether ringing current is needed or not, and switching means efi'ective responsive to a condition indicating a demand for ringing current for closing said circuit connections.

3. In a ringing-current supply system, a transformer having a secondary winding for supplying ringing current and having a primary winding for exciting the secondary winding alternately in opposite directions, a pair of alternative pole changers for controlling the flow of current in the primary winding, means for maintaining both of said pole changers constantly in operation, switching means for applying either operating pole changer to the primary winding to the exclusion of the other, and means periodically efiective for substituting the other pole changer for the currently applied one.

4. In a ringing-current supply system, a pair of alternative pole changers for controlling the flow of ringing current, the demand for ringing current being intermittent, switching means operative responsive to a condition indicating a demand for ringing current for applying one of said pole changers to the system to the exclusion of the other, means for testing the applied pole changer to determine its condition, and means controlled by the said test means responsive to an abnormal condition of the applied pole changer for operating said switching means to substitute the other pole changer for the applied one.

5. In a ringing-current supply system, a pair of alternative pole changers for controlling the flow of ringing current, the demand for ringing current being intermittent, switching means operative responsive to a condition indicating a de-' mand for ringing current for applying one of said pole changers to the system to the exclusion of the other, means for testing the applied pole changer to determine its condition, and means controlled by the said test means responsive to an abnormal condition of the applied pole changer for operating said switching means to substitute the other pole changer for the applied one, an alarm-control conductor, and means for applying a potential thereto dependent upon the last said pole changer being also in an abnormal condition.

6. In a ringing-current supply system, separate ringing circuits, a separate pair of alternative pole changers for each of said ringing circuits for controlling the flow of ringing current therein, the demand for ringing current being intermittent, switching means operative responsive to a condition indicating a demand for ringing current in any of said ringing circuits for applying a pole changer of each of said pairs to its respective ringing circuit,

separate testing means for each ringing circuit for testing the pole changer applied thereto to determine its condition, and separate means in each ringing circuit controlled by the said test means thereof responsive to an abnormal condition of the pole changer applied thereto for bringing about the substitution of the other pole changer of the concerned pair for the applied one.

7. In a ringing-current supply system, a ringing circuit, a pair of pole changers for controlling the flow of ringing current therein, means for maintaining both of said pole changers constantly in operation, both of said pole changers being normally out of effective circuit relation with said ringing circuit, switching means operative responsive to successive occurrences of the same condition indicating a demand for ringing current for operatively placing said pole changers alternately in effective circuit relation with said ringing circuit.

8. In a ringing-current supply system, a ringing circuit, a pair of pole changers for controlling the flow of ringing current therein, means for maintaining both of said pole changers constantly in operation, both of said pole changers being normally out of effective circuit relation with said ringing circuit, switching means operative responsive to successive occurrences of the same condition indicating a demand for ringing current for operatively placing said pole changers alternately in efiective circuit relation with said ringing circuit, means for testing each of said pole changers upon its being placed in circuit relation with the ringing circuit, and means controlled by said testing means responsive to the currently connected pole changer being not in operation when so placed in circuit relation for operating said switching means to substitute the other pole changer.

9. In a ringing-current supply system, a ringing circuit, a pair of alternative pole changers for controlling the flow of ringing current therein, means for applying one of said pole changers to said ringing circuit to the exclusion of the other, means for substituting the other pole changer for the applied one at the end of a predetermined time interval beginning with said application, and means responsive to the flow of ringing current in said circuit for disabling said substituting means.

BERT A. WALLACE. 

